COMPETITIVENESS OF TRANSGENIC OILSEED RAPE

The competitiveness of two transgenic oilseed rape (Brassica napus ssp . napus) lines and their fertile transgenic hybrid was tested in field trials in Belgium and Denmark. The lines contained genes for male ste rility, restoration of fertility and herbicide resistance. The competi tiveness of the three transgenic lines was related to three non-transf ormed commercially-grown oilseed rape varieties: Drakkar, Topas and Li ne. As a reference of a more aggressive crucifer, white mustard (Sinap is alba) was also included in the experiment. The experimental design was a complete block design with two locations, monocultures and mixtu res with barley (Hordeum vulgare), three plant densities, four harvest times and four blocks. The yield density relationship of the transgen ic oilseed rape lines was not different from that of the non-transgeni c varieties in either location. The first harvest times showed a vigor ous biomass production of white mustard, which in turn produced a sign ificant difference in the competitive ability between oilseed rape and white mustard. Later, this difference decreased, and in Belgium there was no difference at the last harvest time. Variations within populat ions may blur actual differences between lines and varieties, and it i s argued that unless the experimental design covers a range of competi tiveness for which it is possible to detect significant differences, t est results reporting a lack of difference between transgenic and non- transgenic plants are of little value.